Navien tankless water heater code E515
PCB fault. Code E515 means the same thing on all 2 Navien series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code E515 means on each Navien series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NPE-2 | PCB fault | Call a pro | $150–$1,100 |
| NPE-A / NPE-S | PCB fault | Call a pro | $150–$1,100 |
Each row opens the full page for that generation. We hold manuals for NPE-2 and NPE-A / NPE-S, and each one gets its own reading of code E515 — what Navien documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Navien wording behind each row, one entry per manual, so you can see where the 2 readings of code E515 agree and where they part company.
NPE-2 — PCB fault
The control board has failed its own checks. Navien's owner-level instruction is worth noting: make sure the electrical cord is properly grounded. Board faults on this unit are often reported alongside grounding problems, so that is checked before the board is condemned.
NPE-A / NPE-S — PCB fault
The control board has reported a fault in itself. Navien gives one owner-facing check and it is worth doing before accepting a board replacement: make sure the electrical cord is properly grounded. A grounding problem can present as a board fault.
Does it matter which Navien you have?
NPE-2 and NPE-A / NPE-S all route code E515 the same way: a professional, at $150–$1,100. That makes it one of the Navien numbers you can act on before working out which unit you own.
Which Navien do you have?
On the 2 series that report code E515, the model number on the rating label starts NPE — match yours against the 13 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Parts, guides and symptoms behind code E515
Code E515 on these 2 Navien series points at 1 part and 2 symptoms, each named by the manufacturer's own procedure for this code.